Tube bending apparatuses and parts therefor



July 29, 1969 D. MAlER ET AL 3,457,753

TUBE [SENDING APPARATUSES AND PARTS THEREl-OR S R m U N m e E E W 4w wm S I w J M t m EH s M 4 I S A0 D J Filed July 18, 1967 ATTORNEYS July 29, 1969 D. E. MAIER ET TUBE SENDING APPARATUSES AND PARTS THEREFOR Filed July 18, 1967 INVENTORS DALE E. MAIER 4 Sheets-Sheet :5

JOSEPH A. CWIK ATTORNEYS July 29,1969 D. E. MAIER ETAL 3,457,753

TUBE BENDING APPARATUSES AND PARTS THEREFOR Filed July 18, 1967 4 Sheets$heet 4 lllll-Ikl ass I9 INVENTORS DALE E. MAIER JOSEPH A. CWIK BY v flaw/y cm ATTORNEYS United States Patent 3,457,753 TUBE BENDING APPARATUSES AND PARTS THEREFOR Dale E. Maier, Evergreen, and Joseph A. Cwilr, Arvada, Colo., assignors, by mesne assignments, to Teledyne, Inc., Los Angeles, Calif., a corporation of Delaware Filed July 18, 1967, Ser. No. 654,110 Int. Cl. B21d 7/04 U.S. Cl. 72-454 38 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to improvements in tube bending apparatuses and improved parts therefor and has particular application for draw forming rectangularly shaped tubes. Such apparatuses and parts therefor incorporate means facilitating the alignment and interlocking of die components relative to each other. Such apparatuses and parts are of a design which permits same to utilize the tube itself in effecting accurate alignment between the cooperating dies. These apparatuses and parts include means for preventing the cooperating dies and the tube which has been draw formed therein from becoming tightly wedged together thereby permitting easy retraction of the dies relative to each other. The clamp die used and these apparatuses include means for assisting in effecting a separation between the clamp die and a tube which has been draw formed. These apparatuses and parts also include means for controlling the amount and location of tube wall growth which occurs during the draw forming operation. This invention also relates to an improved tube bending apparatus and parts therefor which are constructed for draw forming circularly shaped tubes. This particular apparatus includes a clamp die and a pressure die. The clamp die includes a male portion having a first surface and a pair of generally parallel surfaces formed thereon, said parallel surfaces being disposed at a right angle to said first surface, and said first surface having an arcuately shaped, longitudinally extending recess formed therein. The bend die includes first and second recess portions. The first recess portion is constructed to receive either one of a removable grip section and an unbent section of a tube, or an arcuately shaped portion of a bent tube and a hardenable material which upon hardening cooperates with the clamp die to secure the arcuately shaped portion of a bent tube relative to the bend die. The second recess portion is circumscribed in part by a pair of opposed, generally parallel surfaces. The pair of parallel surfaces of the male portion of said clamp die are disposed in abutting and confining engagement with the parallel surfaces of said bend die and intermediate thereof.

BACKGROUND OF THE INVENTION Heretofore, many different apparatuses for draw form ing tubes, pipes and the like have been proposed or are available for use in the industry. Although many of these apparatuses and parts therefor have served beneficially in various applications, it has been found that each have suffered from one or more disadvantages. One of the problems associated with draw forming rectangularly shaped tubes is to prevent the cooperating dies and the 3,457,753 Patented July 29, 1969 draw forming of the rectangularly shaped tubes is that of aligning and interlocking together the cooperating dies. Various dies which have been heretofore proposed have been expensive in construction, complex in operation, and easily damaged or injured thereby necessitating expensive repairs thereto including a reduction in production while awaiting the completion of such repairs. Another problem associated with draw forming rectangularly shaped tubes is that of controlling the amount and location of tube wall growth which occurs within that portion of tube that is subjected to compressive stresses during the draw forming operation.

Where circularly shaped tubes are draw formed, it has been found that often successive sections of such a tube are to be formed and that each successive section either has a different radius of curvature or extends at a different angle as compared with the preceding section or tub- Another problem encountered in prior art devices for draw forming tubes and the like is to produce die components of reduced size and mass. It is well known that the tendency of tool components to warp increases with an increase in the size of mass of the component involved. It is also well known that the problems associated with heat treating tool components likewise increase with an increase in the size of mass of the tool component involved. These problems apply to such tool components as clamp and pressure dies. Thus, due to the requirement of providing interlocking die components, it has been found necessary in the past to increase the overall size and mass of the components involved in order to obtain good interlocking between the cooperating die components. It is also well known that the problems of positioning the cooperating die components with respect to each other increases considerably where tubes having thin walls are involved. The criticality of the problem increases as the thickness of the tube wall decreases.

BRIEF DESCRIPTION OF THE INVENTION It has been found that each of the foregoing disadvantages may be readily overcome through the use of an improved apparatus and parts therefor for draw forming tubes and the like when same are constructed in accordance with the subject invention. More specifically, some of these disadvantages are eliminated through the use of a die, such as a clamp die and a pressure die, for bending rectangularly shaped tubes in a tube bending apparatus in which said die is constructed for engaging a bend die and comprises a first longitudinally extending member having a planar surface formed thereon, said planar surface being constructed for engaging and confining the outer axially disposed wall of the tube to be bent, a second longitudinally extending member having a generally planar surface formed thereon, the planar surface of said second member being disposed generally at a right angle to the planar surface of said first member, said surface of said second member being constructed for engaging and confining one of the radially disposed walls of a tube to be bent, said second longitudinally extending member being constructed for engaging a surface portion of a bend die of a tube bending apparatus thereby facilitating aligning of said die with respect to a bend die. An apparatus for bending rectangularly shaped tubes constructed in accordance with the subject invention includes a bend die having a circumferentially extending recess formed therein, said recess being circumscribed by first, second and third surfaces, said second and third surfaces being disposed in opposed, spaced-apart, generally parallel relationship one with the other, and said first surface being disposed generally at a right angle to said second and third surfaces, and a clamp die and a pressure die, each of said clamp and pressure dies comprising a first longitudinally extending member having a planar surface formed thereon and a second longitudinally extending member having first and second surfaces formed thereon, said first surface of said longitudinally extending member being disposed at a right angle to the planar surface of said first longitudinally extending member, said second surface of said second longitudinally extending member being disposed in abutting contact with a portion of the second portion of the recess formed in said bend die, said clamp die and pressure die cooperating with said bend die to form a rectangularly shaped opening constructed for receiving therein a rectangularly shaped tube.

The problem associated with bending successive sections of a circularly shaped tube is eliminated through the use of a tube bending appartus including a clamp die and a bend die wherein said clamp die includes a male portion having a first surface and a pair of generally parallel surfaces formed thereon, the parallel surfaces being disposed at right angles to said first surface, said first surface having an arcuately shaped, longitudinally extending recess formed therein, said die including first and second recess portions, said first recess portion being constructed to receive either one of a removable grip section and an unbent section of a tube or an arcuately shaped portion of a bent tube and a hardenable material which upon hardening cooperates with the clamp die to secure the arcuately shaped portion of a bent tube relative to the bend die, said second recess being circumscribed in part by a pair of opposed, generally parallel surfaces, said parallel surfaces of the male portion of said clamp die being disposed in abutting and confining engagement with a portion of the parallel surfaces of the bend die and intermediate thereof.

Accordingly, one of the principal objects of this invention is to provide an improved tube draw forming apparatus and parts therefor for aligning and confining a rectangularly shaped tube.

Another object of this invention is to provide an improved tube bending apparatus and parts therefor for aligning and interlocking the clamp and pressure dies relative to the bend die during the tube bending operation and for controlling the amount and location of growth of a tube wall during the tube bending operation.

Another object of this invention is to provide a tube bending apparatus and parts therefor which can be used to form ultra precision rectangularly shaped tubes but which are inexpensive in construction.

Another object of this invention is to provide an improved tube bending apparatus and parts therefor which include means for controlling the amount and location of growth in a tube wall to be bent and means for positioning a tube to be bent relative to the bend die prior to the tube bending operation.

Another object of this invention is to provide an improved tube bending apparatus for bending successive sections or circularly shaped tubes.

Another object of this invention is to provide die components for a tube draw forming apparatus, said components being of reduced size and mass.

Another object of this invention is to provide a tube bending apparatus including a clamp die and a bend die and constructed for bending tubes having, in cross section, a generally circular configuration, said clamp including a male portion having a first surface and a pair of generally parallel surfaces formed thereon, said parallel surfaces being disposed at a right angle to said first surface, said first surface having an arcuately shaped recess formed therein, said bend die including first and second recess portions, said first recess portion being constructed to receive either one of a removable grip section and an unbent section of a tube or an arcuately shaped portion of a bent tube and a material securing the arcuately shaped portion of a bent tube relative to the bend die, said second recess being circumscribed in part by a pair of opposed, generally parallel surfaces, at least a portion of said parallel surfaces of said male portion of said clamp die being disposed in abutting and confining engagement with a portion of the parallel surfaces of said bend die and intermediate thereof.

Another object of this invention is to provide an improved die, such a clamp die and/or a pressure die, for use in bending rectangularly shaped tubes in a tube draw forming apparatus wherein said die is constructed for engaging a bend die, said die comprising a longitudinally extending L-shaped member including first and second longitudinally extending surfaces, said first surface being formed on the stem portion of said L-shaped member, said first surface being generally planar and constructed for engaging and confining a portion of the outer axially disposed wall of the tube to be bent and abuttingly engaging a surafce of the bend die, said second surface being formed on the base portion of the L-shaped member, said second surface being constructed for engaging and confining one of the radially disposed walls of the tube to be bent, the base portion of said L-shaped member being constructed for engaging a second surface portion of the bend die of a tube bending apparatus thereby facilitating the aligning of said die with respect to a bend die.

Another object of this invention is to provide an improved die as aforesaid in which the second surface includes a recess formed adjacent one end thereof, a portion of said second surface being disposed intermediate said first surface and said recess.

Another object of this invention is to provide an improvided die as aforesaid in which said recess has a substantial surface portion disposed within a plane the extension of which forms an included angle with said first surface between approximately 90.25 degrees and degrees, and preferably between approximately 90.25 degrees and 92 degrees.

Another object of this invention is to provide an improved die as aforesaid including means for effecting a separation between said first surface and a tube to be disposed adjacent said first surface.

Another object of this invention is to provide an improved die as aforesaid in which said separating effecting means includes a biased member mounted for reciprocal movement within the stem portion of said L-shaped member.

Another object of this invention is to provide an improved die as aforesaid in which said second surface includes a first planar part disposed perpendicularly to said first surface, and a second planar part disposed within a plane the extension of which forms an included angle with said first surface between approxiamtely 90.25 degrees and 95 degrees, and preferably between approximately 90.25 degrees and 92 degrees, said first planar part being disposed intermediate said first surface and said second planar part.

Another object of this invention is to provide an improved die as aforesaid in which the width of said second planar part is approximately equal to the width of said first planar part.

Another object of this invention is to provide an improved die as aforesaid in which the second planar part of said surface extends from about the neutral axis of the tube to be bent to the inner axially disposed wall of the tube to be bent.

Another object of this invention is to provide an improved die, such as a clamp die and/or a pressure die, for use in draw forming rectangularly shaped tubes in a tube bending apparatus wherein said die is constructed for engaging a bend die, said die comprising a first longitudinally extending member having a generally planar surface formed thereon, said planar surface being constructed for engaging and confining the outer axially disposed Wall of a t ube to be bent, a pair of longitudinally extending members mounted upon said first member in spaced-apart, generally parallel relationship one with the other, said pair of members having opposed surfaces each of which is disposed generally at a right angle to the planar surface of said first member, said opposed surfaces of said pair of members being constructed for engaging and confining a corresponding one ofthe radially disposed walls of a tube to be bent, each of said opposed surfaces of said pair of members being mounted for reciprocal movement of a predetermined limited amount toward and away from each other, each of said pair of members being constructed for engaging corresponding surface portions of a bend die and being disposed intermediate thereof thereby facilitating aligning and interlocking of the die with respect to the bend die.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and advantages will become more apparent from the specification and accompanying drawings in which:

FIGURE 1 is an exploded view, in plan form, showing a tube draw forming apparatus constructed in accordance with the subject invention and including a bend die, a clamp die, a wiper die, and a pressure die;

FIGURE 2 is a schematic View, in cross-section, showing the positioning of a rectangularly shaped tube between a bend die and a clamp or pressure die as shown in FIG- URE 1;

FIGURE 3 is an elevational view of the clamp die taken along line 3-3 of FIGURE 1;

FIGURE 4 is an elevational view of the pressure die taken along line 4-4 of FIGURE 1;

FIGURE 5 is an elevational view of the bend die taken along line 5-5 of FIGURE 1;

FIGURE 6 is an elevational view of the wiper die taken along line 66 of FIGURE 1;

FIGURE 7 is an exploded view, in plan form, of another embodiment of a tube draw forming apparatus constructed in accordance with the subject invention showing a bend die, a clamp die, a pressure die, and a wiper die;

FIGURE 8 is an elevational view of a pressure die taken along line 8-8 of FIGURE 7;

FIGURE 9 is an elevational view of the clamp die taken along line 99 of FIGURE 7;

FIGURE 10 is a right hand elevational view of a bend die shown in FIGURE 7 in combination with a rectangular-shaped tube;

FIGURE 11 is a plan view of a bend die and clamp die for use in bending circularly shaped tubes; and

FIGURE 12 is an elevational view taken along line 12-12 of FIGURE 11.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, in FIGURES 1-6 is shown an improved tube bending apparatus constructed in accordance with this invention and some of the component parts therefor. The tube bending apparatus shown in exploded, plan form in FIGURE 1 comprises a bend die '22, a clamp die 24, a pressure die 26 and a wiper die 28. It will be understood that the bend die 22 is mounted for rotatable movement in a conventional manner.

The bend die 22 has a circumeferentially extending recess 30 formed therein. The recess 30 is circumscribed by first, second and third surfaces 32, 34 and 36, see FIGURE 5. The second and third surfaces 34 and 36 are disposed in opposed, spaced-apart generally parallel relationship with respect to each ot her. The first surface 32 is disposed generally at a right angle to the second and third surfaces 34 and 36. The third surface 36 comprises first and second planar parts 37 and 38, see FIGURE 5. The first planar part 37 is disposed perpendicularly to surface 52 of the clamp die 26 as well as surface of the bend die. The second planar part 38 is disposed within a plane the extension of which forms an included angle with surface 32 between approximately degrees and and 89.75 degrees and preferably between approximately 88 degrees and 89.75 degrees. The second planar part 38 extends radially inwardly from a point adjacent the neutral axis of the tube to be bent until same intersects surface 32. Viewed in a different light, the width of the second planar part 38 is approximately equal to the width of the first planar part 37. As shown, the second planar part 38 is disposed intermediate the first planar part 37 and the first surface 32 of the bend die 22. Preferably, the width of the second surface 32 is less than the width of the third surfaue 34. The bend die also includes a fourth surface 39 which is disposed generally at a right angle to the third surface 34 and extends downwardly therefrom as viewed in FIGURE 5. The bend die has a grip section 40 mounted thereon. The grip section 40 is secured to the bend die 22 through the use of a plurality of bolts 42 and, preferably, one or more dowel pins 44. It will be noted that the recess 30 extends also through the grip section 40-.

In FIGURES 1 and 6 is shown the wiper die 28. The wiper die 28 is generally rectangular in cross sectional configuration. The wiper die 28 has an arcuately shaped surface 46 formed at one end thereof. This surface 46 is constructed for slidably engaging a portion of the first surface 32 of the bend die 22. The wiper die 28 has a plurality of internally threaded recesses 29. One or more bolts (not shown) is threadedly mounted within each recess 29 for the purpose of appropriately mounting the wiper die 28 with respect to the bend die 22.

In FIGURES 1-3 is shown the clamp die 24. The clamp die 24 is used for draw forming rectangularly shaped tubes in a tube draw forming apparatus and is constructed for engaging a bend die such as bend die 22. The clamp die 24 comprises a first longitudinally extending member 50 which has a generally planar surface 52 formed thereon. In FIGURE 2 a portion of the planar surface 52 is shown engaging and confining the outer axially disposed wall 54 of the tube 56, said outer axially disposed wall 54 lying in a plane disposed generally parallel with the axis about which bend die 22 rotates and being subjected to tensive stresses during the bending operation. The clamp die 24 also includes a second longitudinally extending member 58 which has a surface 60 formed thereon. The surface 60 of member 58 is disposed generally at a right angle to the planar surface 52 of member 50. The surface 60 of member 58 is shown in FIGURE 2 as engaging and confining the upper radially disposed wall 62 of the tube 56, said wall 62 lying in a plane extending radially of the axis about which the bend die 22 rotates. The second longitudinally extending member 58 has another surface 64 which engages the surface portion 34 of the bend die 22 thereby facilitating aligning of the clamp die 24 relative to the bend die 22.

Surface 60 of member 58 has a recess 66 formed in the end thereof which is positioned adjacent the tangency of the tube bend, i.e., the approximate point of intersection between vsurface 67 of the wiper die 28 and surface 32 of the bend die 22. A portion of the surface 60 is disposed intermediate the recess 66 and the planar surface 52. Although the surface 66 is shown in FIGURE 1 as being generally pie-shaped, it will be understood that the overall configuration thereof may vary as desired or required and may have a triangular configuration as well. The purpose for recess 66 at this point is to provide a relief area or zone into which the metal of the adjacent tube walls that are under compression during'the draw forming operation may flow. Recess 66 has a substantial surface portion disposed within a plane the extension of which forms an included angle with the planar surface 52 between approximately 90.25 degrees and degrees, preferably between approximately 90.25 degrees and 92 degrees. It will be noted that the clamp die 24 forms, in cross section, an L-shaped configuration in which said first surface 52 is formed upon the stem portion of the L-shaped configuration and said surface 60 is formed upon the base portion of the L-shaped configuration. The clamp die 24 includes additional structure represented by the numerals 70 and 71. The additional structure 70 and 71 is securely mounted with respect to longitudinally extending members 50 and 58 through the use of bolts 72 and dowel pins 73. The clamp die 24 is positioned relative to a platform (not shown) of the tube bending apparatus 20 through the use of suitable means attached to the member 71. The clamp die 24 includes means for effecting a separation between the planar surface 52 and the adjacent wall of a tube such as wall 54 of tube 56. The separating effecting means includes a biased member 68 mounted for reciprocal movement within a recess 69 formed in member 50. The biased member 68, which may be characterized as a pressure pin or spring loaded pin, is appropriately located to exert a force against the center of the wall 54 and, thus, facilitates in urging the tube 56 against the bend die 22 during retraction of the clamp die 24.

In FIGURES 1, 2 and 4 is shown the pressure die 26. The pressure die 26 is generally similar in construction to the clamp die 24. More specifically, the pressure die 26 is used in bending rectangularly shaped tubes in a tube bending apparatus in which the pressure die 26 is constructed for engaging the bend die 22. The pressure die 26 comprises a first longitudinally extending member 74, see FIGURE 4, upon which is formed a planar surface 76. A portion of the planar surface 76 is constructed for engaging and confining a portion of the outer axially exposed wall 54 of the tube 56 in much the same manner as does surface 52 of member 50 of the clamp die 24. The pressure die 26 also includes a second longitudinally extending member 78 which has a surface 80 formed thereon. The surface 80 of member 78 is disposed generally at a right angle to the planar surface 76 of member 74. The surface 80 of member 78 is constructed for engaging and confining one of the radially disposed walls of a tube to be bent, such as wall 62 of tube 56. Member 78 has another surface 82 formed thereon. Surface 82 is constructed for engaging a portion of surface 34 of the bend die 22 thereby facilitating aligning of said pressure die 26 with respect to the bend die 22. The pressure die 26 also includes additional structure represented by the numberals 84 and 86. The additional structure 84 and 86 is securely mounted with respect to members 74 and 78 through the use of bolts 88 and a dowel pin 90. The pressure die 26 is mounted relative to the platform (not shown) of the tube bending apparatus 20 through the use of suitable securing means which are attached to member 86. The surface 80 of member 78 includes a first planar part 92 which is disposed at a right angle to the planar surface 76 of member 74 and a second planar part 94 which is disposed within a plane the extension of which forms an included angle with the planar surface 76 of member 74 between approximately 90.25 degrees and 95 degrees, and preferably between approximately 90.25 degrees and 92 degrees, see FIGURE 4. The first planar part 92 is Y disposed intermediate the second planar part 94 and the planar surface 76. The width of second planar part 94 is approximately equal to the width of the first planar part 92.

Referring now to FIGURES 1 and 2, the tube draw forming apparatus 20 will be ready for receiving and draw forming rectangularly shaped tubes when the wiper die is moved to the right, as viewed in FIGURE 1, until the arcuately shaped surface 46 is disposed in sliding contact with the surface 32, and the pressure die 26 is moved to the right, as viewed in FIGURE 1, until a portion of surface 82 is disposed at the same general level as surface 34 of the bend die 22 but spaced apart therefrom and the right end of the pressure die is disposed adjacent the tangency of tube bend. The tube 56 is fed between the assembled wiper and bend dies and the pressure ard clamp dies until one end thereof is disposed intermediate a portion of surface 52 of the clamp die 24' and a portion of the surface 32 of the bend die 22. Upon actuation of a power driven mechanism (not shown) the clamp and pressure dies are moved toward the bend and wiper dies until portions of the surfaces 64 and 82 of the clamp and wiper dies are disposed in abutting contact with corresponding portions of the surface 34 of the bend die 22. The tube 56 is confined between the bend die 22 and the clamp and pressure dies 24 and 26 during the draw forming operation. Since the surface 8110f the clamp and pressure dies is disposed in opposed relation to the surface 36 of the bend die 22 and since each of these surfaces has a second planar part, said second planar part 38 of surface 36 and planar parts 94 of surface being divergently formed in a direction proceeding toward the center of rotation of the bend die 22, it will now be understood that these surfaces cooperate to form a means for controlling the amount and location of tube wall growth at the tangency of tube bend draw forming operation. As a matter of fact, during the draw forming operation, that portion of the tube walls extending radially outwardly from the neutral axis of the tube during the bending thereof reduces in overall thickness while that portion of the tube walls located radially inwardly of the neutral axis of the tube to be bent increases in overall thickness. Through the use of the recess 66 and planar part 94 of the clamp and pressure dies 24 and 26, respectively, and second planar part 38 of the bend die 22, it will be understood that the portion of the tube walls which is located radially inwardly of the neutral axis of the tube to be bent increases in thickness and thereby substantially fills the void otherwise existing between said recess and planar parts and the corresponding adjacent portion of the tube walls. Where it is desired to keep the internal cross sectional figuration of the tube 56 essentially unchanged during the tube draw forming operation, it becomes necessary to provide, externally of the tube walls, an area or zone within which this growth of the tube walls may occur. It will now be understood that under these condi tions such increase in thickness of the tube walls would effectively confine or wedge the member 80 and the tube 56 within the recess 30 relative of the bend die 22. When this occurs, difficult problems are encountered in separating the clamp and pressure dies from the bend die. However, through the use of the recess and the second planar parts as aforedescribed, it will be readily understood that the clamp and pressure dies are easily and quickly separated from the bend die without damaging the tube 56 in any way or changing the radius of curvature which has been formed.

It will be noted that the tube 56 itself cooperates with the various dies of the tube bending apparatus 20 in effecting a good alignment between the clamp and pressure dies and the bend die but without adversely affecting the interlocking relationship achieved between such dies.

Although the surface 60 is shown formed with recess 66 and surfaces 80 and 36 are shown formed with the second planar parts 94 and 37, it will be understood that such surfaces need not incorporate therein this recess or these second planar parts and, in fact, same are to be omitted entirely where it is desirable or necessary to maintain the external cross sectional figuration of the tube in a rectangular shape, such as is the case in forming various parts for the manufacture of furniture and other aestheti cally appearing items. Under these circumstances, the mandrel (not shown) which is to be disposed within the tube 56 would be suitably formed to provide the desired clearance between the surfaces of the mandrel and the adjacent surfaces of the appropriate wall portions to accommodate the growth of the tube walls of the tube. However, it is to be understood that even in these circumstances, a positive aligning and interlocking relationship is effected and maintained without adversely the ease with which the clamp and pressure dies may be separated or retracted from the bend die.

In FIGURES 710 is shown another embodiment of an improved tube draw forming apparatus 96 constructed in accordance with this invention. The tube bending apparatus 96 shown in exploded, plan form in FIGURE 7 comprises a bend die 98, a clamp die 100, a pressure die 102 and a wiper die 104. The bend die 98 is mounted for rotatable movement in the conventional manner.

The bend die 98 has a circumferentially extending recess 106 formed therein. The recess 1106 is circumscribed by first, second and third surfaces 108, 110 and 112, respectively, see FIGURE 10. The second and third surfaces 110 and 112 are disposed in opposed, spacedapart, generally parallel relationship with respect to each other. The first surface 108 is disposed generally at a right angle to the second and third surfaces .110 and 112. The bend die 98 has a grip section 114 integrally formed thereon. The recess 106 extends also through the grip section 114. The bend die has a removably mounted platelike member 116 mounted upon the bend die 98 adjacent the end of the grip section 114. The removable member 116 is secured relative to the bend die 98 through the use of a plurality of bolts 118, see FIGURE 10. The member 116 has a recess formed therein. The recess is constructed for receiving therein a portion of a tube that is to be bent.

In FIGURES 7 and 9 is shown the clamp die 100. The clamp die 100 is used for bending rectangularly shaped tubes in a tube draw forming apparatus and is constructed for engaging a bend die such as bend die 98. The clamp die 100 comprises a first longitudinally extending member 120 which has a generally planar surface 122 formed thereon. The planar surface 122 is constructed for engaging and confining the outer axially disposed wall of a tube such as wall 124 of tube 126 shown in FIGURE 10. The clamp die 100 also includes a pair of longitudinally extending members 128 and 130 mounted upon said first member 120 in spaced-apart, generally parallel relationship one with the other. The pair of members 128 and 130 have opposed surfaces 132 and 134 each of which is disposed generally at a right angle to the planar surface 122 of the first member 120. The opposed surfaces 132 and 134 are constructed for engaging and confining a corresponding one of the radially disposed walls of a tube such as walls 136 and 138 of the tube 126 shown in FIG- URE 10. Each of said pair of members 128 and 130 is mounted for reciprocal movement of a predetermined limited amount toward and away from each other. In this connection, it will be noted that members 128 and 130 are mounted to member 120 through the use of bolts 140. As shown in FIGURE 9, it will also be noted that each of said members is mounted for limited movement axially of its respective bolt 140. The purpose for this feature will be described later. The opposed surface 132 of member 128 includes a recess 144 formed adjacent the end of the clamp die 100 which is to be disposed adjacent the tangency of tube bend. A portion 142 (see FIGURE 9) of opposed surface 132 is disposed intermediate said recess 144 and said planar surface 122. The opposed surface 134 of member 130 also includes a recess 148 which is similar to and located opposite recess 144 of member 128. A portion 146 (see FIGURE 9) of surface 144 is disposed intermediate said recess 148 and said planar surface 122. It is to be noted that recesses 144 and 148 are generally similar to recess 66 of clamp die 24- and, thus, the criteria relating to recess 66 of clamp die 24 applies equally well to recesses 144 and 148.

In FIGURES 7 and 8 is shown the pressure die 102. The pressure die 102 is generally similar in construction to the clamp die 100. More specifically, pressure die 102 is used in drawing forming rectangularly shaped tubes in a tube draw forming apparatus in which the pressure die 102 is constructed for engaging the bend die 98. The pressure die 102 comprises a first longitudinally extending member 152which has a planar surface 154 formed thereon, said planar surface 154 being constructed for engaging 10 and confining a portion of the outer axially disposed wall such as wall 124 of tube 126 shown in FIGURE 10. The pressure die 102 also includes a pair of longitudinally extending members 156 and 158 which are mounted upon the first longitudinally extending member 152 in spacedapart, generally parallel relationship with respect to each other. The pair of members 156 and 158 has opposed surfaces 160 and 162 formed thereon. Each of the opposed surfaces 160 and 162 is disposed generally at a right angle to the planar surface 154 of the first longitudinally extending member 152. Each of the oppose-d surfaces 160 and 162 is constructed for engaging and confining a corresponding one of the radially disposed walls such as walls 136 and 138 of tube 126 shown in FIGURE 10. Each of the pair of members 156 and 158 is mounted upon the longitudinally extending member 152 by means of a plurality of bolts 164 for reciprocal movement of a predetermined limited amount toward and away from each other. Each of the pair of members 156 and 158 is constructed for engaging corresponding surface portions of the bend die 98 thereby facilitating aligning of said pressure die with respect to the bend die 98. More specifically, a portion of surface 166 of member 156 abuttingly engages a portion of surface while at the same time a portion of surface 168 of member 158 abuttingly engages a portion of the surface 112 of bend die 98. When disposed in this manner, members 156 and 158 will be located intermediate surfaces 111 and 112 of bend die 98.

The surface 160 of member 158 preferably includes a first planar part 170 which is disposed perpendicularly to the planar surface 154 of member 152, and a second planar part 172 which is disposed within a plane the exten ion of which forms an included angle with the planar surface 154 of member 152 between approximately 90.25 degrees and 95 degrees, and preferably between 90.25 degrees and 92 degrees. Similarly, surface 162 of member 158 includes a first planar part 174 which is disposed perpendicularly to planar surface 154 of member 152, and a second planar part 176 which is disposed within a plane the extension of which forms an included angle between the planar surface 154 of member 152 between approximately 90.25 degrees and 95 degrees, and preferably between ap )roximately 90.25 degrees and 92 degrees. The second planar parts 172 and 176 of surfaces 160 and 162 extend from a point adjacent the neutral axis of the tube to be bent to the inner axially disposed wall of the tube to be bent, such as wall of tube 125. The width of the second planar parts of surfaces and 162 are approximately equal to the width of the first planar parts and 174-, respectively. It will be noted that the first planar parts are disposed intermediate said second planar parts and planar surface 154.

As previously described, the pair of members included within the clamp die 100 and the pressure die 102 are mounted to permit one of such members to move toward and away from the other member. There are a number of reasons for mounting this pair of members in this manner. One of the reasons is to reduce the positioning accuracy required for posItioning the clamp and pressure dies relative to the bend die prior to moving the clamp and pressure dies into contacting, aligning, interlocking relationship with respect to the bend die. It will be understood that since each of the pair of members may move toward and away from the other of said pair of members that said members may be accurately positioned within the circumferentially extending recess 106 formed within the bend die even though the clamp and pressure dies are not themselves positioned as accurately as would be required were the pair of members to be rigidly mounted with respect to said clamp and pressure dies. Another reason for mounting the pair of members in this manner is to equalize between each of the members within said pair the wedging or sandwiching force exerted upon each of the members by the tube to be bent and the adjacent portion of the bend die. Equalization of this force between each of the pair of members is effected during the initial aligning operation, during the draw forming operation, and during the retraction of said pair of members from said recess. Such equalization of force between each of the members within the pair has been found to be quite beneficial since it facilitates both the aligning and the removal of the pair of members relative to the bend die by reducing the amount of force which might otherwise be required to effect same and by minimizing or substantially eliminating the increased amount of force which has been heretofore involved in accomplishing the foregoing where one of such members was wedged or sandwiched between the tube and the adjacent portion of the bend die with a greater degree of force than the other of said members. In this connection, it will be understood that where one of such pair of members is more tightly wedged or sandwiched between adjacent portions of the tube and the bend die, than the other member, such member tended to rotate or cant slightly upon removal thereof and this rotation further increased the amount of force required to remove same from its wedged position. Further, not only is the amount of wedging forcing increased but also this increased amount of wedging force tends to move the bent tube itself relative to the bend die thereby adversely affecting the radius of curvature which has been achieved during the draw forming operation. Where the force which wedges one of the pair of members between adjacent surfaces of the tube and the bend die becomes sufficiently great, it has been found that not only is the bent tube drawn outwardly away from the bend die but also the rod connecting the mandrel with a portion of the tube bending apparatus may also bend thereby requiring either a repair or replacement of the mandrel rod as well as resulting in rejection of the piece of bent tube.

Referring now to FIGURES 7 and 10, it will be understood that before the tube 126 is fed into the tube bending apparatus the wiper die will be moved toward the bend die until the arcuately shaped surface 178 thereof is disposed in sliding engagement with the surface 108 of the bend die, and the pressure die 102 is moved toward the clamp die 100. The tube 126 is fed between the assembled wiper and bend dies and pressure and clamp dies until a portion thereof rests Within the recess formed within the removable member 116. In this position, tube 126 is positioned centrally of the planar surfaces 122 and 154 of the clamp and pressure dies 100 and 102 such that when the clamp and pressure dies are moved toward the position tube 126 the pair of members incorporated within each will pass above and below the upper and lower radially disposed walls 136 and 138 of the tube 126. It is to be understood that a mandrel, not shown, will be positioned within the tube 126 prior to the bending operation and maintained therein during the bending operation for the purpose of preventing a collapse of the tube walls during the bending operation.

In FIGURES 11 and 12 is shown another embodiment of a tube bending apparatus constructed in accordance with the subject invention. In FIGURES 11 and 12 are shown a bend die 180, a clamp die 182 and a pressure die 183 which are constructed for draw forming tubes having, in cross-section, a generally circular configuration. The clamp die 182 includes a male portion 184 having a first surface 186 and a pair of generally parallel surfaces 188 and 190 formed thereon. The parallel surfaces 188 are disposed at a right angle to the first surface 186. The first surface 186 has an arcuately shaped, longitudinally extending recess 192 formed therein.

The bend die 180 includes a first recess portion 194 and a second recess portion 196. The first recess portion 194 is constructed to receive either one of a removable grip section 198 and an unbent or substantially straight section (not shown) of a tube, or an arcuately shaped portion (not shown) of a bent tube and a hardenable material (not shown) which upon hardening cooperates with the clamp die 182 to secure the arcuately shaped portion of a bent tube relative to the bend die 180. The second recess portion 196 is circumscribed in part by a pair of opposed, generally parallel surfaces 200 and 202. AS shown in FIGURE 12, the pair of parallel surfaces 188 and 190 of the male portion 184 are disposed in abutting engagement with a corresponding one of the parallel surfaces 280 and 202 which circumscribe the first recess 196 of the bend die 180. The parallel surfaces 188 and 190 cooperate with the parallel surfaces 200 and 202 to align clamp die 182 relative to the bend die and to interlock the clamp die 182 with respect to the bend die 180 to prevent vertical movement of one with respect to the other during the draw forming operation.

In FIGURE 11 is shown a portion of the pressure die 183 which is similar in construction to the clamp die 182. More specifically, the pressure die 183 includes a male portion 204. The male portion 204 comprises a first surface portion 206 which has a longitudinally extending, arcuately shaped recess 208 formed therein. The male portion 204 also includes a pair of parallel surfaces, only one 210 of which is shown, which are disposed at right angles to the first surface portion 206'. The parallel surfaces of said pressure die 183 are disposed in abutting and confining engagement with a portion of the opposed parallel surfaces 200 and 202 which circumscribe a part of the second recess 196 of the bend die 180.

The grip section 198 is disposed within the first recess 194 and is removably mounted therein by suitable means (not shown). The grip section 198 has a longitudinally extending, arcuately shaped surface 212 formed therein. Longitudinally extending, arcuately shaped surfaces 192 and 212 cooperate and form, in cross-section, a generally circular-shaped opening in which is to be disposed at circularly shaped tube that is to be draw formed. It will be noted that the bend die 180 has a circumferentially extending, arcuately shaped surface 214 which merges with the arcuately shaped surface 212 of the grip section 198.

In the tube bending industry there arises on many occasions the necessity of bending successive sections of a tube in which the successive sections have a different radius of curvature and/ or are disposed at a different angle than the preceding section of bent tube. Under these circumstances, it is necessary to secure the first section of the tube which has already been bent relative to the bend die 180 such that a successive section of the tube may be bent. This is easily and readily accomplished with the apparatus shown in FIGURES 11 and 12 by removing the grip section 198 and inserting therein a portion of the tube which has already been bent. Thereafter, the clamp and pressure dies are positioned essentially as shown in FIGURE 11 and a hardenable material is disposed in the first recess 194 and any appropriate portion of the second recess 196. When the hardenable material has hardened, the male portion 184 of the clamp die 182 and the hardened material cooperate to secure relative to the bend die that portion of the bent tube that is disposed within the first and second recess portions 194 and 196 thereby permitting the draw forming of a successive section of such tube in a desired manner. Thus, the apparatus shown in FIGURES 11 and 12 provides for the first time an inexpensive device possessing great flexibility which permits the bending of a single as well as successive sections of a circularly shaped tube.

It is well known that the problems associated with heat treating a tool component and the chances of same warping increase with an increase in the size of mass of the tool component involved. This applies also to such tool components as clamp and pressure dies. In this connection, it will be noted that the overall mass involved in clamp and pressure dies constructed in accordance with the subject invention had been substantially decreased thereby minimizing or substantially eliminating the problems heretofore encountered from a warpage viewpoint and greatly reducing the problems previously associated with heat treating of a tool component.

It is recognized in the tube bending field that the thinner the tube wall involved the more critical will be the aligning of the clamp and pressure dies relative to the bend die. However, in accordance with the concept disclosed herein, it has been found that the problems heretofore encountered with thin wall tubes has been greatly minimized due to the improved aligning characteristics incorporated within tube bending apparatus of this invention and the improved die components therefor.

As previously indicated, several attempts have been made to minimize the alignment, interlocking, and separation of the clamp and pressure dies from the bend dies where the bending of rectangularly shaped tubes are involved. However, most of the devices heretofore proposed for coping with this particular problem involve clamp and pressure dies which were not only expensive to manufacture but also difiicult to use and which were of such design and configuration that same had to be handled with exceptional care both during use and storage if a damage thereto was to be prevented. It will be noted, however, that tube bending apparatus of this invention and the die components therefor are quite inexpensive to manufacture, simple to use and do not require any special or unusual care in use or handling in order to prevent or minimize damage thereto. All of these factors are quite important in effecting optimum tube draw forming performance in an effcient manner.

In view of all the foregoing, it will not be readily apparent that a greatly improved tube bending mandrel and die components thereof have been described and illustrated which may be easily and quickly used with excellent results to draw form rectangularly shaped tubes and that this is true even though the walls of such tubes are quite thin. This has been accomplished by providing a tube draw forming apparatus and die components thereof which readily facilitate aligning, interlocking and separation of the various parts without adversely affecting the surfaces of the tube which is to be or has been bent and without encountering difficult positioning problems of the various die components relative to each other.

It is to be understood that this invention is not limited to the exact embodiments of the devices shown, which are merely by way of illustration and not limitation, as various other forms and modifications will be apparent to those skilled in the art, and it is therefore intended that the appended caims cover all such changes and modifications.

What is claimed is: v

1. A die for use in bending rectangularly shaped tubes in a tube bending apparatus, said die being constructed for engaging a bend die and comprising: a longitudinally extending L-shaped member including first and second longitudinally extending surfaces; said first surface being formed on the stem portion of said L-shaped member, said first surface being generally planar and constructed for engaging and confining a portion of the outer axially disposed wall of a tube to be bent and abuttingly engaging a surface of a bend die; said second surface being formed on the base portion of said L-shaped member, said second surface being constructed for engaging and confining one of the radially disposed walls of a tube to be bent; the base portion of said L-shaped member being constructed for engaging a second surface portion of a bend die of a tube bending apparatus thereby facilitating aligning of said die with respect to a bend die.

2. A die as described in claim 1 in which said second surface includes a recess formed adjacent one end thereof, a portion of said second surface being disposed intermediate said first surface and said recess.

3. A die as described in claim 2 in which said recess has a substantial surface portion disposed within a plane the extension of which forms an included angle with said first surface between approximately 90.25 degrees and 95 degrees.

4. A die as described in claim 3 in which said recess has a substantial surface portion disposed within a plane 14 the extension of which forms an included angle with said first surface between approximately 90.25 degrees and 92 degrees.

5. A die as described in claim 1 including mean for effecting a separation between said first surface and a tube to be disposed adjacent said first surface.

6. A die as described in claim 5 in which said separating effecting means includes a biased member mounted for reciprocal movement within the stem portion of said L-shaped member.

7. A die as described in claim 2 including mean for effecting a separation between said first surface and a tube to be disposed adjacent said first surface.

8. A die as described in claim 1 in which said second surface includes a first planar part disposed perpendicularly to said first surface, and a second planar part disposed within a plane the extension of which forms an included angle with said first surface between approximately 90.25 degrees and 95 degrees, said first planar part being disposed intermediate said first surface and said second planar part.

9. A die as described in claim 8 in which said second planar part of said second surface extends from a point adjacent the neutral axis of a tube to be bent to the inner axially disposed wall of the tube to be bent.

10. A die as described in claim 8 in which the width of said second planar part is approximately equal to the width of said first planar part.

11. A die as described in 8 in which said second planar part of said second surface is disposed Within a plane the extension of which forms an included angle with said first surface between approximately 90.25 degrees and 92 degrees.

12. A die for use in draw forming rectangularly shaped tubes in a tube draw forming apparatus, said die being constructed for engaging a bend die and comprising: a first longitudinally extending member having a generally planar surface formed thereon, said planar surface being constructed for engaging and confining the outer axially disposed wall of a tube to be bent; a pair of longitudinally extending members mounted upon said first member in spaced-apart, generally parallel relationship one with the other, said pair of members having opposed surfaces each of which is disposed generally at a right angle to the planar surface of said first member, said opposed surfaces of said pair of members being constructed for engaging and confining a corresponding one of the radially disposed walls of a tube to be bent; each of said pair of members being mounted for reciprocal movement of a predetermined limited amount toward and away from each other; each of said pair of members being constructed for engaging corresponding surface portions of a bend die and being disposed intermediate thereof thereby facilitating aligning and interlocking of said die with respect to a bend die.

13. A die as described in claim 12 in which each of said opposed surfaces of said pair of members includes a recess formed adjacent one end thereof, a portion of each opposed surface being disposed intermediate said corresponding recess and the planar surface of said longitudinally extending member.

14. A die as described in claim 13 in which each recess has a substantial surface portion disposed within a plane the extension of which forms an included angle with the planar surface of said first longitudinally extending member between approximately 90.25 degrees to 95 degrees.

15. A die as described in claim 13 in which each recess has a substantial surface portion disposed within a plane the extension of which forms an included angle with the planar surface of said first longitudinally extending member between approximately 90.25 degrees and 92 degrees.

16. A die as described in claim 12 including means for effecting a separation between the planar surface of the first longitudinally extending member and a tube to be disposed adjacent said planar surface.

17. A die as described in claim 16 in which said separating effecting means includes a biased member mounted for reciprocal movement within the stern portion of said L-shaped member.

18. A die as described in claim 13 including means for efiecting a separation between the planar surface of said first longitudinally extending member and a tube to be disposed adjacent said planar surface.

19. A die as described in claim 12 in which each of said opposed surfaces of said pair of members includes a first planar part disposed perpendicularly to said planar part disposed within a plane the extension of which forms an included angle with the planar surface of said first member between approximately 90.25 degrees and 95 degrees, said first planar part of each of said opposed surfaces being disposed intermediate a corresponding second planar part and the planar surface of said first longitudinally extending member.

20. A clamp die as described in claim 19 in which the second planar part of each of said opposed surfaces is disposed within a plane the extension of which forms an included angle with the planar surface of said first member between approximately 90.25 degrees and 92 degrees.

21. A die for use in draw forming rectangularly shaped tubes in a tube draw forming apparatus, said die being constructed for engaging a bend die and comprising: a first longitudinally extending member having a planar surface formed thereon, said planar surface being constructed for engaging and confining the outer axially disposed wall of a tube to be bent; a second longitudinally extending member having a surface formed thereon, the surface of said second member being disposed generally at a right angle to the planar surface of said first member, said surface of said second member being constructed for engaging and confining one of the radially disposed walls of a tube to be bent; said second longitudinally extending member being constructed for engaging a surface portion of a bend die of a tube bending apparatus thereby facilitating aligning of said die with respect to a bend die.

22. In an apparatus for draw forming rectangularly shaped tubes and having a bend die, a clamp die, a pressure die and a wiper die, said bend die having a circumferentially extending recess formed therein, said recess being circumscribed by first, second and third surfaces, said second and third surfaces being disposed in opposed, spaced-apart, generally parallel relationship one with the other, and said first surface being disposed generally at a right angle to said second and third surfaces; a clamp die comprising a first longitudinally extending member having a planar surface formed thereon and a second longitudinally extending member having first and second surfaces formed thereon, said first surface of said second longitudinally extending member being disposed at a right angle to the planar surface of said first longitudinally extending member, said second surface of said second longitudinally extending member being disposed in abutting contact with a portion of the second surface of the recess formed in said bend die; and a pressure die comprising a first lon gitudinally extending member having a planar surface formed thereon and a second longitudinally extending member having first and second surfaces formed thereon, the first surface of said second longitudinally extending member of said pressure die being disposed generally at a right angle to the planar surface of said first longitudinally extending member of said pressure die, the second surface of said second longitudinally extending member of said pressure die being disposed in abutting contact With a portion of the second surface of said bend die; said clamp die and pressure die cooperating with said bend die to form a rectangularly shaped opening constructed for receiving therein a rectangularly shaped tube.

23. In an apparatus as described in claim 22, said bend die including a fourth surface disposed generally perpendicular to said third surface, said second surface 16 of said bend die being of lesser width than said third surface of said bend die, and the first surface of the first longitudinally extending members of each of said clamp and pressure dies having a portion thereof disposed in abutting contact with a portion of the fourth surface of said bend die.

24. In an apparatus as described in claim 22 in which the first surface of said second longitudinally extending member of said clamp die includes a recess formed adjacent one end thereof, a portion of said first surface being disposed intermediate said recess and said planar surface of said first longitudinally extending member, said end containing said recess being disposed adjacent one end of said pressure die; and the first surface of said second longitudinally extending member of said pressure die and the third surface of said bend die each comprise first and second planar parts, said first planar parts of each of said surfaces being disposed perpendicularly relative to the first surface and said bend die and the second planar part of each of said surfaces being disposed within a plane the extension of which forms an included angle with the first surface of said bend die between approximately degrees and 89.75 degrees, said second planar part of said third surface of said bend die being disposed intermediate said first planar part and said first surface of said bend die, said first planar part of the first surface of the second longitudinally extending member of said pressure die being disposed intermediate said second planar part and the planar surface of said first longitudinally extending member of said pressure die.

25. In an apparatus as described in claim 24 in which the recess of the first surface of the second longitudinally extending member of said clamp die includes a substantial surface portion disposed within a plane the extension of which forms an included angle with the planar surface of said first longitudinally extending member of said clamp die between approximately 90.25 degrees and degrees.

26. In an apparatus as described in claim 25 in which the width of each of the second planar parts is approximately equal to the width of each corresponding first planar part.

27. In an apparatus as described in claim 22 in which the clamp die includes means for effecting a separation between the planar surface of the first longitudinally extending member thereof and a tube to be disposed adjacent said planar surface.

28. In an apparatus as described in claim 27 in which said separating effecting means of said clamp die includes a biased member mounted for reciprocal movement within the first longitudinally extending member thereof.

29. In an apparatus as described in claim 24 in which the clamp die includes means for effecting separation between the planar surface of the first longitudinally extending member thereof and a tube to be disposed adjacent said planar surface.

30. In an apparatus for draw forming rectangularly shaped tubes and having a bend die, a clamp die, a pressure die, and a wiper die; said bend die having a circumferentially extending recess formed therein, said recess being circumscribed by first, second and third surfaces, said second and third surfaces being disposed in opposed, spaced-apart, generally parallel relationship one with the other, and said first surface being disposed generally at a right angle to said second and third surfaces; a clamp die comprising a first longitudinally extending member having a generally planar surface formed thereon and a pair of longitudinally extending members mounted upon said first member in spaced-apart, generally parallel relationship one with the other, said pair of members having opposed surfaces each of which is disposed generally at a right angle to the planar surface of said first member, each of said pair of members being mounted for reciprocal movement of a predetermined limited amount toward and away from each other, each of said pair of members being constructed for engaging a portion of a corresponding one of the second and third surfaces of said bend die whereby said pair of members is disposed intermediate said second and third surfaces of said bend die thereby facilitating aligning and interlocking of said clamp die with respect to said bend die; and a pressure die comprising a first longitudinally extending member having a generally planar surface formed thereon and a pair of longitudinally extending mmebers mounted upon said first member in spaced-apart, generally parallel relationship one with the other, said pair of members having opposed surfaces each of which is disposed generally at a. right angle to hte planar surface of said first member, each of said pair of members being mounted for reciprocal movement of a predetermined limited amount toward and away from each other, each of said pair of members being constructed for engaging a portion of a corresponding one of the second and third surfaces of said bend die whereby a portion of said pair of members is disposed intermediate said second and third surfaces of said bend die thereby facilitating aligning and interlocking of said pressure die with respect to said bend die; said clamp die and pressure die cooperating with said bend die to form a rectangularly shaped opening constructed for receiving therein a rectangularly shaped tube.

31. In an apparatus as described in claim 30 in which each of the opposed surfaces of said pair of longitudinally extending members of said clamp die includes a recess formed adjacent one end thereof, a portion of each of said opposed surfaces being disposed intermediate said corresponding recess and the planar surface of said first longitudinally extending member, said end of said clamp die containing said recess being disposed adjacent one end of said pressure die; and each of said opposed surfaces of said pair of longitudinally extending members of said pressure die includes a first planar part disposed perpendicularly to the planar surface of the first longitudinally extending member of said pressure die and a sec ond planar part disposed within a plane the extension of which forms an included angle with the planar surface of said pressure die between approximately 90.25 degrees and 95 degrees.

32. In an apparatus as described in claim 31 in which each recess of the opposed surfaces of the pair of mem bers of said clamp die includes a substantial surface portion disposed Within a plane the extension of which forms an included angle with the planar surface of said first longitudinally extending member of said clamp die between approximately 90.25 degrees and 95 degrees.

33. In an apparatus as described in claim 31 in which the width of each of the second planar parts is approximately equal to the width of each corresponding first planar part.

34. In an apparatus as described in claim 30 in which the clamp die includes means for effecting a separation between the planar surface of the first longitudinally extending member thereof and a tube to be disposed adjacent said planar surface.

35. In an apparatus as described in claim 34 in which said separating effecting means of said clamp die includes a biased member mounted for reciprocal movement within the first longitudinally extending member thereof.

36. In an apparatus as described in claim 31 in which the clamp die includes means for effecting separation between the planar surface of the first longitudinally extending member thereof and a tube to be disposed adjacent said planar surface.

37. In a tube draw forming apparatus including a clamp die and a bend die and constructed for draw forming tubes having, in cross section, a generally circular configuration; said clamp die including a male portion having a first surface and a pair of generally parallel surfaces formed thereon, said parallel surfaces being disposed at a right angle to said first surface, said first surface having an arcuately shaped, longitudinally extending recess formed therein; said bend die including first and second recess portions, said first recess portion being constructed to receive either one of a removable grip section and an unbent section of a tube or an arcuately shaped portion of a bent tube and a hardenable material securing the arcuately shaped portion of a bent tube relative to the bend die; said second recess portion being circumscribed in part by a pair of opposed, generally parallel surfaces; and said parallel surfaces of said male portion of said clamp die being disposed in abutting and confining en gagement with a portion of the parallel surfaces of said bend die and intermediate thereof.

38. In a tube bending apparatus as described in claim 37 including a pressure die having a male portion formed thereon, said male portion including a first surface portion having an arcuately shaped, longitudinally extending recess formed therein and a pair of generally parallel surfaces, said parallel surfaces being disposed at a right angle to said first surface portion, said parallel surfaces of said pressure die being disposed in abutting and confining engagement with a portion of the opposed, parallel surfaces which circumscribe a part of said second recess of said bend die and intermediate thereof.

References Cited UNITED STATES PATENTS RONALD D. GREFE, Primary Examiner U.S. Cl. X.R. 72-159 

